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101.
云南绿春地区遥感地质特征与找矿远景综合分析 总被引:1,自引:0,他引:1
针对云南绿春地区地质背景复杂、地形崎岖、植被稠密、传统地面调查方法实施区域地质填图比较困难的问题,利用TM,ETM+和SPOT5多源遥感数据,采用三维可视化等技术提取了该区域地层、岩体和构造的岩性组合、线性构造和环形构造等特征,分析了地质背景,依据构造关系和遥感影像特征分析了区域应力状态;提取了与矿化有关的构造、岩性及羟基、铁染蚀变遥感异常信息,在剖析典型矿床的基础上,进行了找矿预测.取得的研究成果为区域地质填图和矿产勘查工作部署提供了基础地质信息及找矿线索. 相似文献
102.
The ultramafic-hosted Logatchev Hydrothermal Field (LHF) at 15°N on the Mid-Atlantic Ridge and the Arctic Gakkel Ridge (GR) feature carbonate precipitates (aragonite, calcite, and dolomite) in voids and fractures within different types of host rocks. We present chemical and Sr isotopic compositions of these different carbonates to examine the conditions that led to their formation. Our data reveal that different processes have led to the precipitation of carbonates in the various settings. Seawater-like 87Sr/86Sr ratios for aragonite in serpentinites (0.70909 to 0.70917) from the LHF are similar to those of aragonite from the GR (0.70912 to 0.70917) and indicate aragonite precipitation from seawater at ambient conditions at both sites. Aragonite veins in sulfide breccias from LHF also have seawater-like Sr isotope compositions (0.70909 to 0.70915), however, their rare earth element (REE) patterns show a clear positive europium (Eu) anomaly indicative of a small (< 1%) hydrothermal contribution. In contrast to aragonite, dolomite from the LHF has precipitated at much higher temperatures (~ 100 °C), and yet its 87Sr/86Sr ratios (0.70896 to 0.70907) are only slightly lower than those of aragonite. Even higher temperatures are calculated for the precipitation of deformed calcite veins in serpentine–talc fault schists form north of the LHF. These calcites show unradiogenic 87Sr/86Sr ratios (0.70460 to 0.70499) indicative of precipitation from evolved hydrothermal fluids. A simple mixing model based on Sr mass balance and enthalpy conservation indicates strongly variable conditions of fluid mixing and heat transfers involved in carbonate formation. Dolomite precipitated from a mixture of 97% seawater and 3% hydrothermal fluid that should have had a temperature of approximately 14 °C assuming that no heat was transferred. The much higher apparent precipitation temperatures based on oxygen isotopes (~ 100 °C) may be indicative of conductive heating, probably of seawater prior to mixing. The hydrothermal calcite in the fault schist has precipitated from a mixture of 67% hydrothermal fluid and 33% seawater, which should have had an isenthalpic mixing temperature of ~ 250 °C. The significantly lower temperatures calculated from oxygen isotopes are likely due to conductive cooling of hydrothermal fluid discharging along faults. Rare earth element patterns corroborate the results of the mixing model, since the hydrothermal calcite, which formed from waters with the greatest hydrothermal contribution, has REE patterns that closely resemble those of vent fluids from the LHF. Our results demonstrate, for the first time, that (1) precipitation from pure seawater, (2) conductive heating of seawater, and (3) conductive cooling of hydrothermal fluids in the sub-seafloor all can lead to carbonate precipitation within a single ultramafic-hosted hydrothermal system. 相似文献
103.
Miduk hypogene and supergene porphyry Cu–Mo mineralization occurs within the Miocene porphyritic quartz–diorite and host Eocene plagioclase–hornblende phyric andesitic pyroclastic and flow sequence. Both the host rocks were extensively altered by hydrothermal fluids to dominantly potassic, phyllic, and argillic with interstitial to distal propylitic types. 相似文献
104.
笔者结合1/5万磁法扫面及相关磁参数测定工作,在路线地质调查的基础上,进一步对引起江东测区航磁异常的原因进行了客观的分析和总结,得出该区磁异常并非某些专家所讲由"似条带状含铁硅质岩建造(铁多金属矿化)"引起,而实由高黎贡山群中-高级区域变质岩类产生的结论,并对在该区进行地质勘查的找矿标志、矿床类型等找矿方向提出了自己的观点. 相似文献
105.
Field, hand specimen, and microscopic investigations alongside X-ray diffraction analyses revealed four types of hydrothermal alteration (Type-A, -B, -C, and -D) based on the mode of occurrence of altered rocks and alteration mineral assemblage at Hakusui-kyo and Horai-kyo along the Arima-Takatsuki Tectonic Line (ATTL) in western Japan. Type-A alteration locally occurred as gray alteration halos with sulfide minerals. Type-B and -C alterations were confined to fault gouge veins and occurred as greenish-gray veins and brown veins, respectively. Type-C alteration crosscut Type-B alteration. These alterations were associated with a number of granitic fragments including cohesive breccia and micrographic facies. Type-D alteration occurred locally in brown sediments. Different mineralogical features in the four alterations are summarized as (Type-A) illite; (Type-B) chlorite; (Type-C) limonite (Fe3+ hydroxides and goethite) and calcite; and (Type-D) limonite. We propose that the alterations can be broadly divided into Paleocene hydrothermal alteration (Type-A) and post-Late Miocene hydrothermal alteration (Type-B, -C, and -D): Type-A alteration occurred at approximately 200 °C during hydrothermal activity after a granitic intrusion in Late Cretaceous; Type-B, -C and -D alterations occurred under hydrothermal activity accompanying deep fluids with repeated ascents invoked by the seismicity of the ATTL after the Late Miocene. The fluids may have been the “Arima-type thermal waters” (i.e., mixtures of convective groundwater and Na-Ca-Cl-HCO3-type fluids). Type-B alteration occurred in fractures at depths where the temperature was ≥150 °C. Type-C alteration overprinted Type-B alteration as a result of mixing of new deep fluids and descending oxidized meteoric water near the surface. Fe3+ hydroxides and calcite precipitated from the fluids due to the oxidation of Fe2+ and the degassing of CO2, respectively, at ambient to near-boiling temperatures. When the ascending fluids gushed out from the fractures, they generated Type-D alteration at the surface under similar temperature conditions due to the oxidation of Fe2+. 相似文献
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109.
《Chemie der Erde / Geochemistry》2019,79(4):125531
We report new mineralogical, petrographic and noble gas analyses of the carbonaceous chondrite meteorites Y-82162 (C1/2ung), Y-980115 (CI1), Y-86029 (CI1), Y-86720 (C2ung), Y-86789 (C2ung), and B-7904 (C2ung). Combining our results with literature data we show that these meteorites experienced varying degrees of aqueous alteration followed by short-lived thermal metamorphism at temperatures of >500 °C. These meteorites have similar mineralogy, textures and chemical characteristics suggesting that they are genetically related, and we strongly support the conclusion of Ikeda (1992) that they form a distinct group, the CYs (“Yamato-type”). The CY chondrites have the heaviest oxygen isotopic compositions (δ17O ˜12‰, δ18O ˜22‰) of any meteorite group, high abundances of Fe-sulphides (˜10 ‒ 30 vol%) and phosphates, and contain large grains of periclase and unusual objects of secondary minerals not reported in other carbonaceous chondrites. These features cannot be attributed to parent body processes alone, and indicate that the CYs had a different starting mineralogy and/or alteration history to other chondrite groups, perhaps because they formed in a different region of the protoplanetary disk. The short cosmic-ray exposure ages (≤1.3 Ma) of the CY chondrites suggest that they are derived from a near-Earth source, with recent observations by the Hayabusa2 spacecraft highlighting a possible link to the rubble-pile asteroid Ryugu. 相似文献
110.
甘肃白银厂折腰山VMS矿床蚀变带元素迁移及定量计算 总被引:2,自引:2,他引:0
折腰山矿床是甘肃省白银厂矿田内最典型的火山成因块状硫化物(VMS)矿床,赋矿围岩主要为奥陶纪石英角斑凝灰岩,属于FⅡ类流纹岩,为弧后环境的产物,在海底对流循环成矿作用过程中,遭受强烈的热液改造,形成了多种类型的蚀变。文章将折腰山矿床蚀变围岩分为弱蚀变带→绢云母硅化带→绿泥石化带→矿化带,利用蚀变趋势图解和质量迁移计算等方法,定量揭示了热液蚀变过程中元素的迁移规律。研究表明:①从弱蚀变带→矿化带,蚀变强度逐渐增大,主量元素P、Mn有一定活动性,二者的迁移量分别为-8.8%~8.8%和-1.8%~9.9%,但迁移趋势不规律;Si迁移量变化范围较大,为-16.2%~83.73%;Na、Ca、Sr大量迁出,其中Na、Ca最大迁出量分别可达-3.11%和-2.71%;Mg、Fe依次迁入,并在绿泥石化带中达到最大值9.49%和69.73%;K在绢云母化带中迁入量出现峰值1.6%,其后逐渐迁出,最大可达-2.22%;Rb的迁移行为与K一致;②高场强元素Nb、Ta、Zr、Hf等在热液蚀变过程中相对保持惰性;Al、Ti及Y表现为弱活动性;③主要成矿元素Cu随蚀变强度的增大,其迁入量有递增的趋势,Pb、Zn在矿化带中迁入,其余各带均为迁出;④热液活动过程中,SiO_2活化再沉淀,形成硅化蚀变;K的迁入形成绢云母化,并消耗了H~+,使热液酸度减小;Mg、Fe的迁入在还原环境下形成绿泥石化,并伴随金属硫化物的沉淀。因此,折腰山矿床中的绿泥石化可能是导致矿质发生沉淀的重要蚀变作用,其在勘查工作中可以作为寻找VMS矿体的重要标志。 相似文献